In general, if exposed to air or sun light a rubber produces cracks, and particularly if any tensile stress is added the cracks distinctly appear. For the prevention of these cracks so far it has been known to use (1) the antioxidants from amines and (2) those from wax. It is generally said that the former is subjected to a chemical reaction selectively with ozone and consumes the ozone in the surface layer of rubber to prevent the rubber from aging under statical or dynamical conditions, while the latter incorporated in a rubber exudes to the surface to form a thin film, which prevents the rubber from contacting with ozone to produce an antioxidizing effect, particularly under statical conditions. However, usually the above two kinds of agents are used together at the same time.
The antioxidant wax for rubber according to the present invention relates to the latter, namely, the statical antioxidant.
Various antioxidant wax for rubber have been commercially available from old times. For these antioxidant for rubber, however, the function exuding to form a thin film and the tendency in which the once formed thin film peels off and falls away, often varies depending on the used temperature, so that the previous commercial products have had their effective properties one-sided to either one of those temperature regions of higher, lower or medium. In order to improve this drawback there has been proposed an agent of broad carbon number distribution such as from 16 to 41 (U.S. Pat. No. 3,423,348 specification), or an agent which containes the linear hydrocarbons having a carbon number of 26 to 29 in from 25 to 70% and the linear hydrocarbons having a carbon number of 34 to 40 in from 30 to 75% respectively (Japanese Patent Application Publication Gazette No. 25062/1979) and others, but none of these are satisfactory. That is to say, due to their unsuitable carbon to carbon bonding mode and carbon number distribution, those agents have made excessive wax bloom exuded on the rubber surface at a specified temperature and the appearance of rubber surface significantly worse, and at the same time the increased amount of peeled off wax film called for the increased amount of added agents. This resulted in increased effects as plastisizer and deterioration of physical properties, and therefore was not economical.